1. Field of the Invention
The present invention relates to an adsorbent for treating waste water and more particularly to an adsorbent suitable for column packing which is composed of a granular material obtained by subjecting a particular mixture composed mainly of activated sludge to a heat curing treatment and to a granulating operation, which adsorbent can advantageously be used to treat industrial waste water containing ionic or nonionic water pollutants such as heavy metal ions, dyes, surfactants, high molecular weight coagulants and mineral oils.
2. Description of the Prior Art
The waste water disposal system which treats organic waste water such as civil sewage, human waste, industrial waste water, etc. with activated sludge to reduce the BOD (biochemical oxygen demand) and COD (chemical oxygen demand) is one of the waste water purification techniques generally practiced. In this treatment system, a large amount of excess activated sludge is accumulated with the passage of time, so that the disposal of the excess activated sludge is a great problem. Several attempts to utilize such excess activated sludge are being made: the use as a slow-acting organic fertilizer or soil improver because of its richness in the three important elements of fertilizer, i.e. nitrogen, phosphorus and potassium; the use as feed for animals because it is composed mainly of proteins and hydrocarbons; and the use for removing ionic substances in industrial waste water, utilizing its ampho-ionic properties.
In any of the above-mentioned uses, there is extreme difficulty in handling the activated sludge when it is used after it is removed from the treatment process, and particularly, when industrial waste water is subjected to a column treatment which uses activated sludge, it is necessary to granulate the activated sludge. However, activated sludge formed into granules after dehydration and drying has a fatal drawback that the granules are liable to fracture in water, in addition to their having a small mechanical strength (compressive strength, etc.), so that it has been utterly impossible to use such granules for column packing.